19-year-old who makes $10,000 a month from his video game side hustle: 'I never knew that writing could make me' so much money

Unlike professionals who develop characters and plotlines for video game studios, Lahijani specifically writes for users who play Grand Theft Auto 5 Roleplay, a multiplayer computer version of the popular console game. In this iteration of the game, players have to submit character backstories to join specific servers and play with certain users.

He’s earned $62,400 writing more than 400 character backstories for an online version of the video game Grand Theft Auto, according to documents reviewed by CNBC Make It.